Upgrading of oxidic columbiumtantalum materials



. metal production).

Uni d S tes Pa e 3,132,024 UPGRADING OF OXIDIC COLUMBIUM- TANTALUM MATERIALS Louis R. Matricardi, Tonawanda, N.Y., assignor to Union Carbide Corporation, a corporation of New York No Drawing. Filed Oct. 10, 1960, Ser. No. 61,381

3 Claims. (Cl. 7584) This application is a continuation-impart of U.S. patent application 4,864, filed January 27, 1960, now abandoned.

The present invention pertains to a process for producing columbium alloys from oxidic columbium-tantalum starting materials. More specifically the present inven- ,tion pertains to a processfor producing columbium alloys having a higher columbium-tantalum ratio than the columbium to tantalum ratio in the columbium-tantalum oxidic starting materials.

Industry is demanding an ever-increasing volume of low-priced columbium alloys for use in various fields.

. Coupled with' the demand for an increased volume of low' priced columbium alloys is a stipulation for more stringent product quality.

Tantalum is' the major, and most persistent, contaminant of columbium metal and columbium alloys and theseparation of tantalum from columbium is extremely difficult because of the sharp similarity in their chemical L behavior.

Several methodsof solving the tantalum contamination problem have been attempted. They consist of: (l) the employment of natural ores with a high columbiumtantalum ratio; (2) the enrichment of common ores with a high grade columbium oxide (a by-product of tantalum The second method required several refining steps andr is considerably more expensive in view of the cost of high grade, columbium cake and its relative unavailability.

It is an object of the present invention to provide a 3,132,24 Patented May 5,, 1964 greater than 6:1 with an'alloying agent, a fiuxing agent process whereby the columbium-tantalum ratio in colum- 1 bium alloys is upgraded over the columbium-tantalum ratio in' the oxidic starting materials to greater than 200 to 1. r

Other objects will be apparent from the subsequent disclosure and appended claims. 7

The above objects are achieved by, admixing an oxide of columbium and tantalum with an alloying agent, a

fiuxing agent and atleast one reducing agent selected from the group consisting of aluminum and silicon wherein thejamount of the selected reducing agent in less than a I i the efiective amount of reducing agent stoichiometrically required to reduce all the oxidic columbium and tantalum values to columbium and tantalum metal and charging the admixture into a suitable furnace for reduction. 7 'Though the above mentioned process accomplishes the objects of the present invention a more preferred embodi- ,ment of the present invention comprises admixing an oxide source of columbium and tantalum which has been pretreated to remove tin and phosphorus with an alloying agent, a fluxing agent and at least one reducing agent selected from the group consisting of aluminum and silicon wherein the amount of selected reducing agent is substantially less than the eifective amount of reducing agent stoichiometrically required to reduce all the oxidic columelemental aluminum and/or elemental silicon.

V bium and. tantalum values to columbium and tantalum metal and charging the admixture into a suitable furnace tion comprises admixing an oxide of columbium and tan- .7

talum which has been pretreated to remove tin and phosalloy as a reductant.

upgrading the columbium-to-tantalum ratio during reduction of the oxides to metal. Examples of suitable starting materials include columbite and other columbium ores, columbium-tantalum oxide products resulting from metal lurgical beneficiation and concentration processes including flotation and pyrometullurgical processes. The columbium-to-tantalum ratio in the starting mixture is not restrictive to the materials which can be treated in the present process. Some amount of upgrading can be achieved in the final product irrespective of the ratio of columbium-to-tantalum in the starting materials. The preferred starting material contains a columbium-to-tantalum ratio greater than about 6: l; The starting materials containing the higher columbium-tantalum ratios permit upgrading of the columbium-tantalum ratio in .the final alloy without excess loss in the total recovery of columbium metal during reduction.

The preferred oxidic columbium-tantalum star-ting materials also preferably contain only small amounts of tin and phosphorous. These may be removed by beneficiation, either physical and/or pyrometallurgical, prior to use in the present process. Although the presence of tin and phosphorous in the oxidic columbium-tantalum starting materials of the present process is not detrimental to the process of upgrading the columbium-tantalum ratio it may in some instances be desirable to produce a final alloy containing none or only small amounts of these elements. a

The alloying agent may be any element or group of elements which would serve to pick up the reduced columbium and tantalum metal. The use of an alloy pickup material introduces another facet of the present invention, namely, the fact that a useful columbium alloy is produced in the process concurrent with the upgrading of the columbium-tantalum ratio. Examples of a suitable alloying agent would be iron added in the form of iron scrap, iron shot, steel scrap, iron oxide, nickel shot, nickel oxide, or

agent is defined as encompassing scrap, oxides and pure metals which contain a suitable alloyingelement as delineated above. The oxides are-readily reduced during reduction of the columbium values. q

The reduotants employed the present process are In some instances it may be desired to use an-allurninurn-silicon Since the present process empioys less than stoichiometric amounts of reducing agents, the amount of residual reductant in the final product is low. 7 a The stoichiometric amount of reductants utilized in the present process is a most critical consideration. It has been found that decreasing stoichiometric amounts of reduotants cause a progressive increase intthe patio of ool-um'b-iumtantalum in the final alloy. This relationship is more fully shown in the following Table III by specific figures.

3 The amount of reductant utilized in the present process can be noted in several ways. For the purposes of this application the amounts of reducer supplied refers to the total amount of reducerchargedinto the starting amount of reducer employed in the process, it is most meaningful to use the term effective reducer as the term relating to the reductant.

A fluxing agent is employed in the present process to aid in forming and regulating the acidity of the slag. The acidity of the slag in turn determines slag viscosity, melting point, reactivity with the furnace lining and other factors known to contribute to the successful openation of a metalslag metallurgical process. The acidity of the slag is preferably maintained within the range of from 1.2 to 0.60 weight ratio of CaO plus MgO to A1 or within the range of from 1.0 to 2.0 weight ratio of 0210 plus MgO to SiO The amount of fluxing agent added is adjusted accordingly.

An accelerator, such as sodium chlorate (NaC1O may be used to aid in the support of self-sustained exothermic reactions by producing a substantial amount of additional heat in addition to acting as a fiuxing agent.

Since accelerating agents such as NaClO are commonly used the metallurgicalindustry as fluxes as well as heat sources, the choiceof fiuxing agents is governed by well formulated practice and hereinafter the term fluxing agent will be construed to encompass such accelerators.

Table I shows the analysis of the starting Cb-Ta source. The starting mixture as shown in Table II was heated by an electric arc furnace in a magnesia lined crucible to conduct the reduction reaction. After the re-,

action began the remaining portion of the starting mixture was charged into the magnesia crucible and allowed (Al) Aluminothcrrnio. (Al) Aluminothermic power.

to re act. After the reaction was completed the slag and resulting columb-ium form and nickel alloys were tapped 1nto molds to solidify.

Table I Run N o. Columbite Analysis, Percent Cbz05 65. 78 67. 80 67.00 67. 00 T9405- 5. 68 5. 76 5.08 5. 08 TiO 2. 94 1. 84 2. 08 2. 08 FeOU 3.60 3.53 3. 53 3. 53 M110 2.08 2.01 1. 80 1. 86 SnO 0.08 0. 05 0.07 0.07 5102.. 1.16 1.10 0.78 0.78 Garbo 0. 02 0.01 0. 03 o. 03 Zl'Og (0st.) 0.40 0. 30 0.30 0.30 Mixture Components (Pounds):

Fused Columbite 300 300 100 500 Alloying Agent:

Steel Scrap 43 Iron Scale- 48 47 Armco Iron Reducing Agent:

Grained Aluminum Aluminum Shot. Fluxing Agent:

Lirnc 72 90 Sodium Chlorate. 30 15 Percent of stoichiornctric reg duced supplied Process used 1 81. 6 1 81. 2 2 64. 0 2 67.0 'Percent effective reducer 81. 6 77.1 59. 5 55.8 Cb-Ta. ratio in ore 0. :1 0. 92:1 11. 26:1 11. 26:1 Cb-Ta ratio in product 10. 9:1 28. 4:1 103. 0:1 148. 4:1

An analysis of the tinalproduct is provided in the following Table II.

' Table II Product Analysis, Percent Carbon 0:

The following Tables HI and IV illustrate the use of nickel as an alloying agent in the present process.

Table III Mixture Components (Pounds) Run No. 5

Fused Columbitc 500. Alloying Agent:

Electrolytic Nickel 95.

Nickel Oxide 39. Reducing Agent:

Aluminum Shot; 99.

Fluxing Agent:

Lime 48. Percent of stoichiometric reducer suppliocL- 65 (Al) Alumino thonnic. Percent effective rcducen. 9. 5. Cb-Ta ratio in ore 0.70:1. Ob-Ta ratio in product 74.411.

Analysis of the final product is provided in the following Table IV.

The criticality of the present process lies in the selection of the proper amount of reducing agent with reference to the columbium-tantalum analysis of the starting material. It has been found that a decrease in the amount of reducing agent to as low as 54% of the effective stoichiometric amount requred to effect the complete reduction of the columbium and tantalum leads to an upgrading of the columbiuni to tantalum ratio in the final product to values as'high as 200 to 1.

It has also been found that the higher the columbium to tantalum ratio in the starting material, the higher the ratio in the final product for a given amount of effective sults of severalruns similar to that shown in Table I above.

use of decreasing amounts of reductant.

I Table V Effective Aluminum Ratio columbium-tantalum reducer, percent: in product From the above Table V it appears that the ratio of columbium to tantalum will continue to increase with the In actuality, though successively decreasing amounts of reductant below about 55 percent effective reducer may be utilized to attain higher columbium to tantalum ratios, the limit of the amount of reductant would be largely dictated by economics for it is known that the use of below about 55 percent eflfective reducing agent results in an excess amount of unreduced columbium oxide passing to the slag. This fact is not a restriction on the operability of the present process but is a consideration in the economics of the present process.

What is claimed is:

1. A process for increasing the columbium to tantalum ratio in columbium alloys over the columbium-to-tantalum ratio in oxidic columbium-tantalum starting materials comprising admixing a columbium-tantalum oxidic starting material, suflicient fluxing agents to maintain a slag having at leastone of the weight ratios selected from the group consisting of weight ratios from about 1.0 to about 2.0 of C20 plus MgO to SiO and from about 1.2 to about 0.60 of CaO plus MgO to A1 0 material selected from the group consisting of iron oxides, iron,

' nickel oxides and nickel and at least one reducing agent selected from the group consisting of aluminum, silicon and alloys consisting of aluminum and silicon wherein said reducing agent is supplied in an amount ranging from about 40 percent to 90 percent of the effective stoichiometric amount of reducing agent required to reduce all the said columbium and tantalum oxides to columbium and tantalum metal; heating the admixture to a sulficiently high temperature and for a sufficient time to fuse said admixture and to cause reduction of said columbium oxide in the admixture whereby a columbium alloy is produced, said columbium alloy having a substantially greater ratio of columbium to tantalum than said columbium-tantalum oxidic starting material.

2. A process for increasing the columbium-to-tantalum 1 ratio in columbium alloys over the columbium-to-tantalum ratio in oxidic columbium-tantalum starting materials comprising admixing a substantially tin and phosphorous material selected from the group consisting of iron oxides,

iron, nickel oxides and nickel, suflicient fluxing agents to maintain a slag having at least one of the weight ratios selected from the group consisting of weight ratios from about 1.0 to about 2.0 of CaO plus MgO to Si0 and from about 1.2 to about 0.60 'of CaO plus MgO to A1 0 and at least one reducing agent selected from the group consisting of aluminum, silicon and alloys consisting of aluminum, silicon wherein said reducing agent is supplied in an amount ranging from about 40 percent to 90 percent of the eflfective stoichiometric amount of reducing agent required to reduce all the said columbium and tantalum oxides to columbium and tantalum metal; heating the admixture to a sufliciently high temperature and for a sufiicient time to fuse said admixture and to cause reduction of said columbium oxide and continuing said reduction until a substantiallytin and phosphorous free columbium alloy is produced, said columbium alloy having a greater ratio-of columbium-to-tantalum than said columbium-tantalum oxidic starting material.

3. A process for treating columbium-tantalum oxidic starting materials having a columbium-to-tantalum ratio of greater than about 10:1 to produce columbium alloys having columbium-to-tantalum ratios in excess of about 80:1 comprising admixing a columbium-tantalum oxidic starting material having a columbium-to-tantalum ratio of greater than about 10:1, material selected from the group consisting of iron oxides, iron, nickel oxides and nickel, sufiicient fluxing agents to maintain a slag having at least one of the weight ratios selected from the group consisting of weight ratios from about 1.0 to about 2.0 of CaO plus MgO to SiO and from about 1.2 to about 0.60 of CaO plus MgO to A1 0 and at least one reducing agent selected from the group consisting of aluminum, silicon and alloys consisting of aluminum and silicon wherein, said reducing agent is supplied in an amount ranging from about 40 percent to about percent of the effective stoichiometric amount of reducing agent required to reduce all the said columbium and tantalum oxides to columbium and tantalum metal; heating the admixture to a sufiiciently high tempearture and for a sufiicient time to fuse said'admixture and to initiate reduction of said columbium oxide and continuing said reduction until-a columbium alloy haw'ng a columbiumto-tantalum ratio of greater than :1 is produced.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A PROCESS FOR INCREASING THE COLUMBIUM-TO-TANTALUM RATIO IN COLUMBIUM ALLOYS OVER THE COLUMGIUM-TO-TANTALUM RATIO IN OXIDIC COLUMGIUM-TANTALUM STARTING MATERIALS COMPRISING ADMIXING A COLUMBIUM-TANTALUM OXIDIC STARTING MATERIAL, SUFFICIENT FLUXING AGENTS TO MAINTAIN A SLAG HAVING AT LEAST ONE OF THE WEIGHT RATIOS SELECTED FROM THE GROUP CONSISTING OF WEIGHT RATIOS FROM ABOUT 1.0 TO ABOUT 2.0 OF CAO PLUS MGO TO SIO2 AND FROM ABOUT 1.2 TO ABOUT 0.60 OF CAO PLUS MGO TO AL2O3, MATERIAL SELECTED FROM THE GROUP CONSISTING OF IRON OXIDES, IRON, NICKEL OXIDES AND NICKEL AND AT LEAST ONE REDUCING AGENT SELECTED FROM THE GROUP CONSISTING OF ALUMINUM, SILICON AND ALLOYS CONSISTING OF ALUMINUM AND SILICON WHEREIN SAID REDUCING AGENT IS SUPPLIED IN AN AMOUNT RANGING FROM ABOUT 40 PERCENT TO 90 PERCENT OF THE EFFECTIVE STOICHIOMETRIC AMOUNT OF REDUCING AGENT REQUIRED TO REDUCE ALL THE SAID COLUMBIUM AND TANTALUM OXIDES TO COLUMBIUM AND TANTALUM METAL; HEATING THE ADMIXTURE TO A SUFFICIENTLY HIGH TEMPERATURE AND FOR A SUFFICIENT TIME TO FUSE SAID ADMIXTURE AND TO CAUSE REDUCTION OF SAID COLUMBIUM OXIDE IN THE ADMIXTURE WHEREBY A COLUMBIUM ALLOY IS PRODUCED, SAID COLLUMBIUM ALLOY HAVING A SUBSTANTIALLY GREATER RATIO OF COLUMBIUM TO TANTALUM THAN SAID COLUMBIUM-TANTALUM OXIDIC STARTING MATERIAL. 